Why bees always have a safe landing

Graceful and acrobatic motions would be well suited to aircraft design

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When bees approach an object, they steadily slow down to a stop by adjusting their speed as the size of their target looks larger. This technique could help engineers design a new generation of automated aircraft.

Whether landing on a picnic table, underneath a flower petal, or on a wall of a hive, bees always manage to touch down without crashing or tumbling.

Now, for the first time, scientists have figured out how these insects maneuver themselves onto all sorts of surfaces, from right side up to upside-down.

The bees' technique, which depends mostly on eyesight, may help engineers design a new generation of automated aircraft that would be undetectable to radar or sonar systems and would make perfectly gentle landings, even in outer space.

"This is something an engineer would not think of while sitting in an armchair and thinking about how to land an aircraft," said Mandyam Srinivasan, a neuroscientist at the Queensland Brain Institute at the University of Queensland and the Australian Research Council's Vision Centre in Brisbane. "This is something we wouldn't have thought of if we hadn't watched bees do their landings."

When bees approach an object, according to previous work, they steadily slow down to a stop by adjusting their speed as the size of their target steadily looks larger. Srinivasan wanted to know what happens after that.

Along with colleagues, he set up a platform that could be adjusted to any angle from horizontal to vertical and even upside-down.

Using sugar water, the scientists trained honeybees to fly to the platform again and again. Then, the researchers turned on the high-speed camera.

Their footage showed that no matter how flat or steep the surface, bees slow to a hover at 13 millimeters (about half an inch) away from wherever they're going to land. That suggests, Srinivasan said, that the insects are somehow using their eyes to measure that specific distance.

If their landing surface was flat, the researchers report today in the Journal of Experimental Biology that bees simply touched down back legs first.

If the platform was anywhere between vertical and upside-down, on the other hand, the insects made contact with their antennae first, by pointing them almost perpendicular to the platform. Then, the bees hauled their front legs up and finished with a flip-like maneuver to get their mid-legs and rear legs onto the surface.

It's a graceful and acrobatic motion that would be well suited to aircraft design, Srinivasan said. Current landing systems use radiation-emitting systems, which are detectable and often undesirable for military applications.

Existing technologies, the bee work suggests, may also be more complicated than they need to be.

"It's a beautiful way of landing using biological autopilot," he said of the bees. "We would like to make spacecraft that do smooth, flawless dockings. Whatever bees are doing must be computationally simpler than what we are doing now."

A honeybee's brain is the size of a sesame seed and weighs about a milligram. Yet, bees and other insects manage to perform complicated tasks, including smooth upside-down landings.

Figuring out the rules that simple animals use to translate vision into motion, Douglas Altshuler, a biologist at the University of California, Riverside, said, could help engineers design machines that mimic nature in unexpected ways.

"(A machine) doesn't have to look like an animal to use the rules that animals use," he added. "It's trying to recreate the brain instead of recreating the wings."